| With the development of industrialization,water shortage and water pollution have become increasingly prominent.Under this background,membrane separation technology emerges as the times required,providing environmental protection,high efficiency,low energy consumption and sustainable solutions for water treatment.In order to promote the large-scaled application and development of advanced separation membranes,researchers optimized and reduced the thickness of the selected layer to reduce the mass transfer resistance and improve the permeability of the membrane under the premise of ensuring high rejection.However,there are still some defects in the construction of ultra-thin separation membrane,such as the challenges of improving controllability and stability.Moreover,with the rapid development of industrialization,more organic waste liquid is discharged,which not only pollutes water resources,but also wastes recyclable organic solvents.Therefore,the organic solvent resistant nanofiltration membrane has also attracted extensive attention of researchers.However,the requirements of nanofiltration membrane materials are very high when they are used in high concentration,especially in strong polar organic solvent environment.Thus,the nanofiltration membrane materials which can be used in complex organic solvent environment also need technical breakthrough.Herein,the strategy of combining biomimetic dopamine with traditional methods was used to prepare nanofiltration membranes to construct a highly efficient ultra-thin separation layer on porous support membrane,and prepared ternary biomimetic co-coating water system nanofiltration membrane,cyclodextrin biomimetic solvent-resistant nanofiltration membrane and metal organic framework biomimetic multifunctional water and organic solvent nanofiltration membrane.The novel nanofiltration membrane with high throughput and excellent stability in water and organic solvent system was obtained.Through the competition between covalent bond and coordination bond in the coating solution system of polyphenols(PPh)/aminated material(AS)/metal ion(TMIn+),the structure of the selective layer was skillfully regulated to form a uniform ultra-thin(?33 nm)ternary system coating.The influences of concentration,ratio and reaction time of biomimetic ternary co-coating system on the structure of nanofiltration membrane and the coating mechanism were systematically studied.The influence mechanism of biomimetic ternary co-coating system on the hydrophilicity,pollution resistance,permeance and rejection of nanofiltration membrane was expounded by using physical and chemical properties characterizations.Furthermore,the separation efficiency of the typical dyes by the biomimetic ternary system nanofiltration membrane was further investigated and optimized.When the reaction time was 6 h,the PEI concentration at 0.6 wt.% and Co2+ concentration at 0.05 mol L-1,the p DA/PEI/Co2+composite nanofiltration membrane exhibited the best performance.The permeance of the nanofiltration membrane reached 104 L m-2 h-1 bar-1 and 114 L m-2 h-1 bar-1 with completely rejection CR and BTB.It is an order of magnitude higher than the traditional commercial nanofiltration membrane and also has possessed excellent long-term stability and acid-base stability.The solvent resistant composite nanofiltration membrane was further prepared using supramolecular chemistry to regulate the coating reaction of the biomimetic material.Dopamine and cyclodextrin(?-CD)were introduced into the polyamide nanofiltration membrane to construct an organic solvent resistant nanofiltration membrane.The surface structure,hydrophilicity,surface charge and pore structure of the membrane were characterized by Infrared Spectroscopy(FT-IR),Photoelectron Spectroscopy(XPS),Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM),Zeta potential and Ultraviolet-Visible(Uv-Vis)spectrum.When the optimum concentration of ?-CD was 0.6 wt.% and the coating time was 3 h,the Methyl blue/Ethanol(MB/Et OH)permeance of p DA/?-CD membrane was 2.98 L m-2 h-1 bar-1.Compared with the previous p DA solvent resistant membrane,the permeance of Et OH increased by 331% with the addition of ?-CD.In addition,p DA/?-CD membrane can continuously filter MB/Et OH and MB/acetone solutions at room temperature for 20 h,and the separation performance was stable.After 10 cycles test,the permeance of the membrane for Et OH and the rejection of MB remained unchanged,which also showed that the p DA/?-CD membrane had excellent longterm stability and repeatability.The biomimetic nanometer nanofiltration membrane with high permeance was prepared using the natural materials glucose as the water phase monomer and Ui O-66 or Ui O-66-NH2 as additives combined with the dopamine.After the introduction of Ui O-66-NH2 into the p DA-glucose selective layer,the permeance increased by 136.8%(from 13.3 L m-2 h-1 bar-1 to 31.5 L m-2 h-1 bar-1)while ensuring the high rejection of Na2SO4.Ui O-66 and Ui O-66-NH2 enhanced the permeance of solvent without sacrificing the dye rejection with different sizes and charges.The permeance of all solvents including N,N-dimethylformamide(DMF)was higher than 15 L m-2 h-1 bar-1,and the rejection of bengal rose red(RB)was higher than 98%.The reaction mechanism of small glucose with MOF and the improvement mechanism of nanofiltration membrane performance were studied.The results of molecular dynamics simulation and FT-IR showed that glucose interacted with-NH2 of Ui O-66-NH2 to form hydrogen bond and amide bond.The existence of hydrogen bond and amide bond made Ui O-66-NH2 uniformly disperse in the membrane,providing additional molecular transport channels.With DMF activation,the permeance of Et OH and acetone in p DA-glucose/Ui O-66-NH2 membrane were further enhanced with the high RB rejection.The permeance of Et OH increased by 22%,from 24.8 L m-2 h-1 bar-1 to 30.2 L m-2 h-1 bar-1,and the permeance of acetone increased by 15%.In addition,the p DA-glucose/Ui O-66-NH2 composite nanofiltration membrane had good anti-pollution property and excellent long-term stability,and it can maintain high separation efficiency after long continuous operation(Et OH 50 h and DMF 240 h)before and after DMF activation. |
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